Class 必须在内部创建新对象，无法从单元测试访问

Question

我们有一个class，其目的是改变接收到的对象的某些字段的值并保持其其他字段的值

public void process(SomeType someObject) {
  SomeType modifiedObject = modifyObject(someObject);
  nextClass.process(modifiedObject);
}

private SomeType modifyObject(SomeType someObject) {
  String someValueFromServiceCall = someService.getSomeValue(...);
  SomeType modifiedObject = new SomeType.Builder()
                                        .withSomeFieldValuesFromSomeObjectItself(...)
                                        .withSomeFieldValuesFromServiceCall(someValueFromServiceCall)
                                        .build();
  return modifiedObject;
}

SomeType 是遗留的 class，我们可以仅使用其构建器 class 创建它，它没有 setter 方法。这意味着我们不能修改接收到的 someObject 本身，但必须从 modifyObject() 构建和 return 一个新的 SomeType 对象，然后 main 方法可以将其传递给处理下一个 class

然而，这似乎会在单元测试期间引发问题。我们似乎无法从单元测试 class 访问内部 modifiedObject 并且我们似乎无法对其进行 expects/asserts

SomeType someObject = createSomeObjectForTest();
expect(someServiceMock.getSomeValue(...)).andReturn(SOME_VALUE);
expect(nextClassMock.process(someObject)).andReturn(...); //this is not someObject, but the new internal modifiedObject created within underTest
underTest.process(someObject);
assertEquals(someObject.getSomeField(), SOME_VALUE); //this is not someObject, but the new internal modifiedObject created within underTest

Answer 1

ArgumentCaptor 的使用方法如下：

// mock and make sure all fields required for modify are set
SomeType arg = create(); 
ArgumentCaptor<SomeType> captor = ArgumentCaptor. forClass(SomeType.class);

sut.process(arg) ;

verify (nextClass). process(captor.capture());
SomeType modified = captor.get();

Class 必须在内部创建新对象，无法从单元测试访问

Class has to create new object internally, which can't be accessed from unit test

java

junit

unit-testing

junit4

junit5